Tubulars within a wellbore are exposed to highly corrosive acidic conditions. Depending on the types of treatments and the nature of formation damage, the aqueous acidic solution can be hydrochloric acid (HCl), hydrochloric-hydrofluoric mud acid (HCl-HF), organic acids such as acetic acid and formic acid as well as combinations thereof.
For instance, in well stimulation operations, such as pickling, acid washing, matrix acidizing and acid fracturing, an aqueous acidic solution may be applied to the production zone in order to increase the size of the pores within the formation penetrated by the well and to provide enlarged passageways for hydrocarbon, water or steam. Such solutions may also be introduced into the well in order remove formation damage during well completions or subsequent workovers.
Corrosion may also be caused by treatment fluids (such as drilling fluids and completion fluids) having a high salt content.
Corrosion of metallic surfaces during well treatment operations is thus a prominent issue, as evidenced by surface pitting, embrittlement and loss of metal. Corrosion is exacerbated by elevated temperatures and pressures encountered in deeper formations. The cost of repairing or replacing corrosion-damaged casing, tubing, and other equipment in the wellbore is extremely high.
Various corrosion inhibitors for diminishing the corrosive effects on metal surfaces have been developed and used previously in well treatment operations. The types of corrosion inhibitors vary depending upon the nature of the compositions, the types of metal surfaces involved, associated environmental conditions, and the like. In some prior attempts to reduce corrosion by using corrosion inhibitors, various problems exist, such as high toxicity ratings or not being environmentally friendly. Some prior art corrosion inhibitors are also cationic, which makes them incompatible with various other acid treatment additives, such as with anionic anti-sludge agents.
A need exists for new and useful compositions for inhibiting or preventing corrosion during well treatment operations with safer, less toxic, and more environmentally acceptable compositions. It is also desirable for the compositions to be compatible with other additives that are used in acid treatments.
It should be understood that the above-described discussion is provided for illustrative purposes only and is not intended to limit the scope or subject matter of the appended claims or those of any related patent application or patent. Thus, none of the appended claims or claims of any related application or patent should be limited by the above discussion or construed to address, include or exclude each or any of the above-cited features or disadvantages merely because of the mention thereof herein.
Accordingly, there exists a need for improved compositions which inhibit corrosion and having one or more of the attributes or capabilities described or shown in, or as may be apparent from, the other portions of this patent.